Synthesis of cyclooctadiene-1, 5



Patented Apr. 2. .9, 1952 2,594,889 SYNTHESIS OF CYCLOOCTADIENE-1,5

Richard M. Elofson, Ponoka, Alberta, Canada, assignor to General Aniline & Film Corporation, New York, N. Y., a corporation of Delaware N Drawing. Application December 31, 1949, Serial No. 136,399

2 Claims.

The present invention relates to the preparation of cyclooctadiene-1,5 by the reduction of cyclooctatetraene.

The eight-membered ring compound cyclooctatetraene (CaHa) is now readily available through the polymerization of acetylene in the presence of a nickel catalyst.

Cyclooctatetraene has been subjected to selective hydrogenation (Reppe PB62543) to produce either cyclooctene or cyclooctane. It is exceedingly difficult, however, to prepare from cyclooctatetraene either cyclooctadiene or cyclooctatriene by direct hydrogenation.

cyclooctadiene-1,5 has been prepared previously by dehalogenation of the dimer of chloroprene according to the method of Cope and Bailey, described in the Journal of the American Chemical Society, vol. 70, page 2308. It has also been formed by the distillation of quaternary hydroxides of des-dimethyl-granatanin according to the method of Willstatter, Berichte, vol. 38, page 1976.

Neither of these methods, however, has been found to be very satisfactory. They are both costly and produce the desired cyclooctadiene in relatively low yields. For instance, the method of Cope and Bailey is reported as produ-cingthe cyclooctadiene-1,5 in a yield of about 56% and along with a polymeric residue.

I have now discovered that cyclooctadiene-1,5 can be readily obtained in very good yields by the reduction of cyclooctatetraene by means of an alkali metal in a low boiling aliphatic alcohol. The end result of this procedure is rather surprising, to say the least, for, as is well understood, oleflnes and polyolefines are not usually reducible with the aforestated reagents.

The envisaged procedure has great appeal not only from the standpoint of the high yield and the cheapness of the process but also from the standpoint of the purity of the cyclooctadiene obtained. Thus it has been found that by the process contemplated, practically pure cyclooctadiene is obtained without the production of other reduction products such as cyclooctane, cyclooctene or cyclooctatriene which would normally be expected to appear in the reaction mixture.

The production of cyclooctadiene-1,5 in a relatively pure state and in high yield by the reduction of cyclooctatetraene with an alkali metal in a low boiling aliphatic alcohol constitutes the purposes and objects of the present invention.

The reduction of the cyclooctatetraene is effected by heating the same with an alkali metal such as sodium, potassium or lithium in a low boiling aliphatic alcohol preferably to reflux. As an alcohol suitable for the process, reference may be made to methanol, ethanol, propanol, butanol, and the like.

The invention is further illustrated by the following examples, but it is to be understood that the invention is not restricted thereto.

Example I Into a 1-liter, S-necked, round bottom flask equipped with stirrer and reflux condenser were placed 400 ml. of absolute ethanol and 30 g. of cyclooctatetraene. To this solution was added with refluxing 38.5 g. of sodium metal. After the addition of sodium, the mixture was refluxed for 1 hour or until all of the sodium had reacted. The mixture was cooled and sodium ethylate was precipitated. 300 ml. of water were added with cooling. The solution was then extracted three times with ml. of low boiling petroleum ether. The extracts were dried over anhydrous magnesium sulfate and the petroleum ether distilled ofi through a small column.

26 g.:86.6% of a colorless liquid was obtained. Fractionation gave B. P. of 144-148 (3.; Refractive index-4.4864.

Analysis: Cal. C:88.89%, H:l1.l1%

Found C:89.22%, H:11.10%

Example II The procedure is the same as in Example I, excepting that the ethanol was replaced by an equivalent quantity of methanol.

Example II I The procedure is the same as in Example I, excepting that the sodium was replaced by an equivalent quantity of potassium.

The product produced by the above procedures is undoubtedly cyclooctadiene-1,5. In the product obtained the double bonds are not conjugated, ior the product does not form a maleic anhydride adduct. Ozonolysis and nitric acid oxidation produces succinic acid. In addition, the physical properties, such as the refractive index, boiling point, and the like, approximate those reported in the prior literature.

The cyclooctadiene-1,5 is readily reactive, absorbing 2 moles of hydrogen to produce cyclooctane, melting at 10.5 C., and having a refractive index of 1.4566.

It also absorbs 2 moles of bromine to form a product of the empirical formula C8H12B14, having a melting point of 127-128 C;

Various modifications of the invention will 3 4 occur to persons skilled in this art, and I therefore do not intend to be limited in the patent EFERENCES CITED granted except as necessitated by the appended The following references are of record in the file of this patent:

0 mm: 5 1. The process of producing cyclooctadiene-LS Polymenzation of Acetylene to FIAT which comprises heating cyclooctatetraene with final e (PB 62,593) pages 45 and an alkali metal in a low boiling aliphatic alcohol. avallable May 1947- 2. The process of producing cyclooctadiene-Lfi which comprises refluxing a, reaction mixture of 10 cyclooctatetraene, sodium metal and ethanol.

RICHARD M. ELOFSON. 

